1. Fields of the Invention
The present invention relates to a thin metal casing with plastic parts and a manufacturing method thereof, especially to a thin metal casing attached with a thermoplastic rubber (TPR) adhesive layer on a surface thereof and then the TPR adhesive layer is connected with plastic parts by injection molding. The TPR adhesive layer is a thermoplastic rubber layer synthesized by butadiene-styrene block copolymer and hydrocarbon petroleum resin. The plastic parts, the TPR adhesive layer and the thin metal casing are integrated firmly to form an integral composite structure by pressure and temperature of injected material during injection molding.
2. Descriptions of Related Art
There are various products available on the market, especially electronics including, but not limited to, computers such as notebook computers, communication products such as mobile phones, consumer products (so-called 3C products), etc. They all include a thin casing used as a housing that covers all the components therein. The structure of the thin casing varies according to the design requirements of the product. According to materials for a base of the thin casing, the thin casing includes two types—a thin plastic casing and a metal thin casing.
The thin plastic casing with a decorative outer surface is generally produced by in-mold decoration process (IMD). A substrate that is 3-dimensional and printed with figures such as a plastic film is mounted into a mold. The substrate (plastic film) is called IMD film hereafter. Then thermoplastic resin is injected by plastic injection molding technique to form a base of the casing on the rear side of the IMD film and the base is called resin base. The resin base and the IMD film are connected to form an integral thin plastic casing. The IMD film is fixed and connected to the outer surface of the resin base to form a permanent device. The IMD film is used as a decorative outer surface for the thin plastic casing, a protective surface for the thin plastic casing or both. Moreover, the protective surface for the can also be temporarily fixed on the outer surface of the resin base to form a temporary device. After completing the production, the IMD film is peeled off. The printed figures on the IMD film are transferred to or embossed on the outer surface of the resin base to form a decorative outer surface of the thin plastic casing.
There are many techniques related to the structure design and manufacturing method of the thin plastic casing mentioned above.
Refer to U.S. Pat. No. 3,654,062, a molded decorative plaque including a body portion of a plastic material and a facing sheet disposed over the front face of the body portion is produced by injection molding. The thermoplastic is injected into a mold on a rear side of the facing sheet. As to U.S. Pat. No. 6,117,384, a printed substrate with at least one color is fit into a mold and then a molten resin is injected into the mold cavity through gates behind the printed substrate to produce a one-piece permanently bonded three-dimensional product. In the U.S. Pat. No. 4,391,954, a thermoplastic molding composition comprising an aromatic carbonate polymer and a polyester derived from a cycleohexanedimethanol is revealed. The U.S. Pat. No. 6,465,102 reveals an article that includes a formed polymeric base with a decorative surface area and a process for making the molded structure. The polymeric base comprises a transparent cycloaliphatic polyester resin that is free from an aromatic moiety and the method of molding thereof. In the U.S. Pat. No. 6,117,384, an improved in-mold decorating process (IMD) for the manufacture of plastic articles is disclosed while the U.S. Pat. No. 6,136,441 reveals techniques related to multilayer plastic articles. Refer to the patents that reveal structure design or manufacturing method related to the plastic housing mentioned above, it is learned that most of the techniques place a further limitation on the IMD film and the resin base respectively. For example, the IMD film or the resin base is restricted to be made from plastic with a specific chemical group. Thus an integral composite plastic board in which the film and the base are connected firmly and difficult to peel off is produced. Each patent is distinctive from other patents.
However, when the IMD film and/or the resin base of the thin plastic casing formed by composite materials are/is placed with a further limitation, not only the materials used are restricted, the applications of the IMD film and/or the resin base are also limited. This has negative effect on the applications of the produced thin plastic casing. For example, once users want to use different materials to produce the IMD film such as fabric, leather, resin fiber, etc for diversity of products, the same technique or equipment is unable to be used for manufacturing the products with high production efficiency, ease in mass production, and good quality control. Thus the use efficiency and applications of the plastic housing are unable to be improved. These are disadvantages of the plastic housing.
As to the common thin metal casing, it is generally produced by machining of a metal sheet such as aluminum alloy sheet. The thin metal casing can be further treated by surface processing to have gloss or patterns. Moreover, a protective resin layer such as resin film is arranged over the outer surface of the metal housing to avoid damages in use such as scratches, bumps, etc. Or a resin layer with figures is arranged at the outer surface of the metal housing for protecting and improving the appearance or texture of the product. For assembling components inside the product, plastic injection molding technique or injection molding attachment is used to dispose or attach various plastic components such as flange or rib on a certain position of an inner surface (metallic surface) of the thin metal casing. Thus the structure of these plastic components is simplified, the whole thickness is reduced and the structural strength is improved.
There are various techniques related to the structure design and manufacturing method of the thin metal casing mentioned above available now, including U.S. Pat. No. 5,695,699, U.S. Pat. No. 5,472,782, US App. Pub. No. US2009/0117401, US2008/0127479, US2007/0218721, etc.
Refer to Chinese Pat. App. No. ZL02805359.1 (PCT/JP2002/007267, WO2003/064150), a composite material of aluminum alloy and resin and a production method therefore are revealed. As a pre-treatment, a rib is immersed in at least one aqueous solution selected from ammonia, hydrazine, hydrazine derivative and water-soluble amine compound. Then the rib is inserted into an injection molding die used to inject it. A thermoplastic resin composition is filled in the surface of a metal frame by injection molding to form a rib. A molded cover enclosure includes integrally joined metal frame and ribs of a thermoplastic resin composition and having the features of metal in terms of strength and external design. Moreover, the interior of the enclosure can be produced with complicated shape and structure.
Refer to Chinese Pat. App. No. ZL200380102886.0 (PCT/JP2003/014213, WO2004/041532), a composite article of aluminum alloy with resin and a method for production thereof are revealed. The composite article includes a thermoplastic resin composition containing polyphenylene sulfide as a component and adhered to the surface of a shaped article of an aluminum alloy. The method includes a pretreatment comprising immersing the shaped article of an aluminum alloy in an aqueous solution of at least one selected from among ammonia, hydrazine and a water-soluble amine compound.
Refer to Chinese Pat. App. No. ZL200380104500.X (PCT/JP2003/014214, WO2004/041533), a composite of aluminum alloy and resin composition and a process for producing the same are revealed. The composite is characterized by comprising an aluminum alloy shaped item having a surface roughness of 5 to 50 μm or more, the surface provided with 1 μm or less fine depressions or protrusions, and a thermoplastic resin composition composed mainly of a polyphenylene sulfide or polybutylene terephthalate resin whose average of lengthwise and crosswise linear expansion coefficients is in the range of 2 to 4×10−5° C.−1. The thermoplastic resin composition is penetrating and anchored in the depressions or protrusions.
Refer to Chinese Pat. App. No. ZL200680046075.7 (PCT/JP2006/324493, WO2007/066742), an aluminum alloy-resin composite and a method of producing the same are revealed. The composite is formed by an aluminum alloy-based material and resin component. An aluminum alloy-based material is dipped in a corrosive aqueous solution such as ammonia, hydrazine, or water-soluble amine compounds to form microconcaves coating the surface. The average radius of the microconcaves is ranging from 10 nm to 80 nm. As the resin component, it includes polyamide resin compounded and a material having improved shock resistance. The aluminum alloy-based material is inserted into an injection molding die and the polyamide-based resin composition is injected onto the surface thereof to give an integrated composite product.
However, the above patents all relate to a composite material formed by metal and resin and a manufacturing method thereof and feature on that the metal (such as aluminum alloy) is immersed in a special aqueous solution (such as water-soluble amine). Then thermoplastic resin with specific ingredients is attached and integrated to a surface of the aluminum alloy by injection molding. In other words, the treatment of the metal (aluminum alloy) and the ingredients of the resin are both specified and restricted. Thus the manufacturing method and the application of the composite material are limited. This has negative effect on use efficiency and application of the metal housing. Especially most of the specific aqueous solution used doesn't match environmental requirements. The thin metal casings and manufacturing methods thereof mentioned above have following shortcomings: In the injection mold, a pouring opening is designed corresponding to each plastic part for performing injection under high pressure at fixed points. During the plastic injection molding process, the thin metal casing is easy to get deformed or damaged and the difficulty in manufacturing of the injection mold is increased. Moreover, the metal surface of the thin metal casing needs to be soaked in specific aqueous solution and this makes the manufacturing process more complicated and has negative effect on mass production of the thin metal casing. The specific aqueous solution also causes environmental problems.
As to Taiwanese Pat. App. No. 85100575 (Pub. No 404888), a metal sheet covered by resin and having high distinctness of image and excellent adhesion during processing is revealed. A metal sheet is used as a substrate and is covered by resin. At one side of the substrate, a coating layer, a modified acrylic resin layer with a thickness of 5˜100 μm, a patterned and/or printed layer, an adhesive layer, and a polyester-based resin film with a thickness of 5˜100 μm arranged in sequence therefrom (refer to claim 1). The modified acrylic resin layer is formed by polypropylene copolymer 100˜20 parts by weight and polypropylene 100˜0 parts by weight. Or the substrate is disposed with a coating layer, a patterned and/or printed layer, a modified acrylic resin layer with a thickness of 5˜100 μm, an adhesive layer, and a polyester-based resin film with a thickness of 5˜100 μm in turn (refer to claim 2). Or the substrate is installed with a coating layer, a modified acrylic resin layer with a thickness of 5˜100 μm, an adhesive layer, and a polyester-based resin film with a thickness of 5˜100 μm in turn (refer to claim 3). Or the substrate is set with a coating layer, a modified alkene layer with a thickness of 5˜100 μm, and a transparent polyester-based resin film with a thickness of 5˜100 μm in sequence (refer to claim 4). However, the ingredients of the laminated resin layer have been specified and limited and the main purpose is to make the metal sheet covered by the resin have high distinctness of image. Thus the shape of the metal sheet is also limited and this has negative effect on the application of the metal housing produced by the metal sheet.
Refer to Taiwanese Pat. App. No. 86106332 (Pub. No. 434145) “metal sheet coated with resin and having higher definition, reflectivity and good adhesion”, a metal sheet covered with resin is revealed. The metal sheet covered with resin includes a metal sheet used as a base, a transparent soft resin layer, an adhesive layer with pigments, a transparent resin film having two sides with gloss finish. The arithmetic mean deviation Ra of the roughness of the metal sheet is between 0 and 10 micrometers. The transparent soft resin layer can be uncured mixed type resin layer, coating cover layer made from polyester resin, or polyolefin resin. At least one surface of the metal sheet is covered by a coloring layer, the soft resin layer, the adhesive layer and the transparent layer in turn from the metal sheet to the transparent resin film. However, the ingredients of the resin coated the metal sheet are limited and the main purpose is to make the metal sheet covered by the resin have high reflectivity. Thus the shape of the metal sheet is also limited and this has negative effect on the application of the metal housing produced by the metal sheet.
Refer to Taiwanese Pat. App. No. 093119015 (Pat. Grant No. I280190) “method for forming electronic metal housing and structure of the same”, an aluminum alloy substrate disposed with a film layer focused on improvement of shortcomings of two prior arts is revealed. The method includes a step of coating adhesive, a step of firing and heating, a step of rolling and pressing and a step of cooling and forming. Firstly, coat adhesive on a surface of at least one side of a metal substrate made from aluminum alloy and the adhesive has metal powders. Then heat the metal substrate coated with the adhesive to make the adhesive become soft. A film layer is rolled and pressed over the adhesive by a heated roller. The film layer consists of at least one polyvinylchloride (PVC) layer, an adhesive layer, and a polyester layer laminated to each other in turn. The adhesive layer also includes metal powders. After cooling, the film layer and the metal substrate are connected to each other tightly. However, the ingredients of the film layer laminated on the surface of one side of the aluminum metal substrate including the PVC layer, the adhesive layer, and the polyester layer arranged in turn are specified and limited. Thus the shape of the metal substrate is restricted and this has negative effect on the application of the thin metal casing.
Refer to Taiwanese Pat. App. No. 093210282 (Pat. Grant No. M261368) “metal plate of electronic housing”, it also has shortcomings of restrictions on the film layer as mentioned in the above Taiwanese Pat. App. No. 093119015 (Pat. Grant No. I280190).
Refer to Taiwanese Pat. App. No. 097208521 (Pat. Grant No. M345706) “composite metal sheet”, a composite metal sheet including a metal substrate, a composite resin adhesive layer and a pressed layer laminated on a metal sheet over the composite resin adhesive layer. Thus the metal sheet and the metal substrate are connected with each other tightly. However, the two outer sides of this invention include the metal sheet and the metal substrate, both are being specified and restricted.
Refer to Taiwanese Pat. App. No. 096215339 (Pat. Grant No. M328384) “metal with environmental protection laminate”, the metal with the environmental protection laminate includes at least one metal substrate, an adhesive layer coated on at least one surface of one side of the substrate, and a film layer formed by a polyurethane (PU) bottom layer and a PU surface layer. The adhesive layer can be softened by being heated. A roller is used to roll and press the film layer on the adhesive layer. Then after cooling, the film layer and the metal substrate are connected firmly. However, the film layer formed by the PU bottom layer and the PU surface layer has been specified and defined. Thus the appearance or texture of the metal substrate is restricted and this is bad for the application of the metal housing produced by the metal with the film.
Thus the techniques available for composite boards have certain shortcomings. There is room for improvement and a need to provide a novel structure of the composite board and a method for manufacturing the same that overcomes the shortcomings of the prior arts ZL02805359.1, ZL200380102886.0, ZL200380104500.X and ZL200680046075.7, etc.